of the Cuzco Valley, Peru. 



25 



ably modified by volcanism and by the deposition of glacial 

 debris. 10 The relatively flat-lying area immediately north of 

 the city of Cuzco, embracing the pampas of Pucro, Kkallac- 

 haca, Era, Yucay, and Ccorao, with a combined area of approx- 

 imately 12 square miles, may be called the Limestone plateau 

 (fig. 13). From an elevation of 13,000 feet at the base of 

 Cerro Seneca its surface slopes east and south to the 11,500- 



Fig. 13. 



Fig. 13. General view of the Limestone Plateau, Pucro Pampa, 

 looking north-eastward across the upper canyon of the Huatanay. 



foot contour line. The bedrock on which the plateau is 

 developed is limestone of the Yucay formation, which is 

 believed to owe its preservation to the presence of the Huancaro 

 and Tticapata faults, by means of which a block including the 

 calcareous strata was brought below the general level. It is 

 probable that at the time of regional base-leveling the limestone 

 plateau formed part of the Inca peneplain and that its present 

 position, 1,000 feet below the peneplain, is largely the result 

 of erosion. 

 10 See p. 39. 



